Many or most integrated circuit (“IC”) packages encounter delamination after the moisture loading requirement of 85° C. & 85% humidity for a duration of 168 hours, as specified by JEDEC MSL (“Moisture Sensitivity Level”) testing. In this contest, delamination refers to a separation between silver plated leadfinger areas and a mold compound, due to poor adhesion between the mold compound and the silver plated areas. Silver plating is known to having a smooth surface and thus the molding compound often does not adhere properly to the plated areas. Delamination may affect the IC packaging, resulting in package and wire bond weaknesses during reliability testing, such as when stress is applied to the package, e.g., due to moisture, temperature or humidity. Delamination may also result tin product field failures such as broken or lifted wire bonds.
Thus, there is a need for eliminating leadfinger delamination in IC packages, such as 8L SOIC & 28SOIC semiconductor device housings, for example. The JEDEC requirement mandates zero delamination on wire bonding areas using palladium coated copper wire at MSL 1, which rating indicates that the devices is not moisture sensitive. Components must be mounted and reflowed within the allowable period of time (floor life out of the bag). One way to reduce or eliminate the leadfinger delamination is to downgrade the devices to MSL3, which rating defines a maximum of one week exposure to ambient conditions before the device is assembled on a PCB. However, this typically adds substantial cost to the parts and requires special handling of the parts by the customer when removing the parts from moisture barrier bags.
Another approach intended to address this problem is to remove the silver plating on lead frame to allow the molding compound to increase the adhesion with the copper surface of the lead frame. This helps reduce the delamination but does not solve the problem, as silver plating is required for wire bonding.